Reflection elimination device



May 14, 1940. J. M. ROPER v 7 2,200,300

REFLECTION ELIMINATION DEVICE Filed Aug. 4, 1937 INVENTOR JOHN M. DOPER yaw am .ATTORNEY Patented May 14, 1940 UNITED STATES PATENT OFFICE Application August 4,

1 Claim.

1937, Serial No. 157,377

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) This invention relates to a reflection elimination device and has for an object to provide means of eliminating reflections of lighted objects from nearby reflecting surfaces. The invention has particular application for use in airplanes and it is likewise usable in analogous positions in other vehicles such as boats, automobiles, locomotives and the like.

In operating an airplane the pilot must continually observe the instruments as well as his path of travel. At night it is necessary that the instruments be lighted in order that they may be visible. The windshield'protecting the pilot necsarily acts to reflect images of the lighted instruments under ordinary conditions, making it diffi cult for the pilot to observe landmarks and other objects through the windshield and seriously increasing the hazard of operation. Pilots often flnd it necessary to extinguish the lights on the instrument board in order to properly observe the landmarks. This, of course, has the hazard in that the pilot does not have the information of the instruments available simultaneously as it is necessary. I

The use of polarized eye glasses has been suggested in order to eliminate the glare of the image 'refiections in the windshield but such glasses have the undesirable effect of likewise diminishing the amount of light that may reach the pilots eyes,

thereby diminishing his vision in all directions.

With this invention it becomes possible to eliminate the reflections of the lighted instruments in the windshield so that the pilot may have full use of his lighted instruments and simultaneously have full use of his vision in observing landmarks through the windshield. and this is accomplished by lighting the instrument by indirect lighting and placing a polarizing medium only between the lighted surface of the instrument and the observer so that only the reflected light from the instrument passes through the polaroid.

With the foregoing and other objects in View, as will hereinafter become apparent, this invention comprises the combinations, constructions and arrangements of parts hereinafter set forth and illustrated on the accompanying drawing wherein:

Fig. l is a fragmentary plan view of an instrument board to which this invention has been applied.

Fig. 2 is a side view of Fig. 1, and

Fig. 3 is a top plan schematic view of an airplane cockpit showing the windshield and instrument board to which this invention has been applied. There is shown at 10 a vehicle instrument on an instrument board H on which is also mounted a lighting means [2 for lighting the face of the instrument, as will be observed in Fig. 2. Raysfrom the lighting means i2 may reach the face l3 of the instrument both directly as at H and. indirectly as at I5 when reflected from the inside of the instrument shield Hi. This instru-v ment shield I6 also serves as a mounting means for a polarizing screen H, the polarizing screen I! being rotatably adjustable as at l8 over the face i3 of the instrument H]. The plane polarized light emitted by the polarizing screen l'l will be reflected back into the cockpit, or refracted outwardly through the windshield and consequently rendered invisible to the observer, in a proportion depending upon the nearness of approach to a right-angle-relation between the plane of polarization of screen I! and the plane of polarization by reflection of the windshield. Screen I! is rotatably -mounted in supporting shield 5, providing means to adjust said screen to the most effective angle with respect to the planes of the Windshields to eliminate annoying reflections.

In operation, the polarizing screen [1, when rotatably adjusted, will at least in one position eliminate any reflections of the face i3 of the instrument i 0 in the Windshields l9 and 20. Sufficient illumination so as to make the faces of the instruments distinctly visible to the operator will reach his eyes at all times, yet due to the polarization of such light no reflected images of the instruments will appear in the Windshields thereby avoiding any interference with the vision of the operator through the windshield and avoiding interfering with maximum efliciency. It will i be further noted that the operator sees his instruments by polarized light only but that he sees all other objects by normal vision undisturbed by the presence of reflections in the Windshields. Safety of operation of an airplane is thereby greatly enhanced. v

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or ,therefor.

I claim:

Means for preventing reflected images of an instrument face lighted with unpolarized artificial light from being visible in the windshield of a vehicle to the operator of the vehicle, the light source being invisible to the operator, said refleeting images preventing means comprising a polarizing screen, said screen providing a window in parallel relation to the instrument face, the

light rays from the light source reaching the instrument face without passing through said polarizing screen window, said polarizing screen window being mounted for rotation in the plane thereof parallel to the instrument face, the vehicle windshield being at an analyzing angular relation to the polarizing screen window and th instrument face, and means under the control c the operator for rotating said polarizing scree window to the optimum position.

JOHN M. ROPER. 

